VocabularyDiameter: The diameter is any straight line that passes through the center point of a circle and the end points lie on the circle.
Radius: The radius is a line from the center point of a circle to an end on the circle itself. Circumference: The circumference is the perimeter around the circle, the measurement of the circle itself. |
Today's Target: Understand the formula for calculating the circumference and area of a circle with Pi.
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PiPi is a unique number. As some of you know already, the image to the right is the symbol for "Pi." Pi is considered an "Irrational number" because it is endless and does not have a repeating number pattern.
If we wrote Pi out as a number, we would write down 3.14 However! Keep in mind that 3.14 is not even close to the whole value of pi. Pi is an irrational and endless number. We round pi to the hundredth because writing out the whole number for our math problems is absurd. If your calculator has it, you can also use the π symbol to make your calculation more accurate. For most problems, using pi to the hundredth decimal is more than enough. |
FormulasFinding the circumference and area of circles involves these two formulas:
Distance around the circle C = π x d Circumference = Pi x Diameter Area within the circle A = π x r ² Area = Pi x (Radius x Radius) Remember BEDMAS. This formula is a two step problem, using multiplication and exponents. We use BEDMAS here and solve the exponent rule first, then multiply with pi afterwards. |
Examples
Questions
Go through the following questions to find the circumference or area. These questions will be handed in at the end of the lesson. Calculator usage is recommended.